Vapor generator



Dec. 16, 1952 M FRlsCH 2,621,637

VAPOR GENERATOR 54 #wher/N edc/1 ATTORNEY' 2 sHEETs-sm'r 2 IFJ.;

D ec. 16, 1952 MVr-'RISCH 'VAPOR GENERATOR Filed Aug. 20, 1946 Patented Dec. 16, .1952

VAPORGENERATOR MartinFrisch, New York, N. Y., assgnorto Foster Wheeler Corporation, New York, N. Y., a clorporati'on'of NewYork Application. August 20, 1946, SerialN o.; 69.13824 .a

This -invention relatesto vapor generators and more particularly. v to vapor generators of the oncefthrough type.

Thepresent invention as applied to thel generation of steam, provides a once-throughforced circulationv vapor generatorin whichthe separation. of steam from the .circulating water is effected mechanically by rapidy rotation. of .sepa-. ratingmeanswhich are-operativewith the circulatingpump or pumps and in which. thehighly concentratedwater separated from the, steamis fed.. to a .vapor generating` section of said vapor generator.`

In.. the.A -preferred arrangement I of the present invention, the-separatingand circulating means for delivering` water to a'steam generatngsection is of. the type disclosed in my co-penoling4 applicationY for Unitedy States Patent vSerial No. 418,650, led November 12, 1941, now Patent No. 2,405,573, in whichV the circulatingpumpr is driven, after the generator is started, kby steam flowing` from the separator. In my above-mentioned type of circulating and separating device, an. auxiliary Water turbinevr is Avutilized to drive. the circulating. pump -by feed Water. to assure immediate and adequate circulation when thev generator. is-started, the feed water used'. for actuatingsaid. auxiliary pumprbeingj returned` tothe suction of the feed pump or to some intermediate. stage thereof. The once-through forced-y circulation generator of the present.inventionv may be. controlled manually in :the samemanner a natural circulation steam' generator is controlledor it may be controlled automatically,

The inventionwill be understood from the following, description when. considered I. in con-- nection with the accompanying drawing. forming a part 'thereof and in which:

Fig; 1 is a more or less diagrammatic viewy of a'steam generator embodying the present inven. tion withv parts thereof in vertical section;

Fig. 2"is anA enlargedV vertical'sectional View of' the upp'erportionofithe separating and cirf culatingdeviceshown in Fig..1, andA Fig.Y 3 is a vertical sectional View of'the. lower por-tion ofthe separatingand circulating device.

Like charactersv of reference refer to' like parts throughout the several'views.

Referring'to the drawings, the Vapor generator shown' diagrammatically at A comprises a set.

ting. lufhaving burner means Il'at one end' I 2' thereof. The burnerv is supplied with air for combustion through a fan I3;.the gases of vcom-- bustionfrom the burner. flowing through the. settingIU-fiom the end" I2 thereof toward' the 2.. opposite-end. I4 through which Opposite-end the gases .y pass from ythe setting'.

Anevaporator or rst .Vapor generating VSection. I5 is positioned adjacent tlleblllfllel en@ I2-of the setting. Theirst evaporator'section I 5His shown diagrammatically; and comprises a fluid ,owrath I6 having aninlet landen Outlet.

I8. Disposed beyond in thedirectionpfiipw ofthe gases f Combustion aladin.. spagedrela; tionshipm with the first evaporatorsectiQll; I;is a -second evaporatoror second vvaper generating section. I9 y which comprises a` fluid owfpa'ih v2B in the path 0f OWxOf .theeases-Which-lowratn has .an inlet 2| and an outlet 22.V The inletof theA second evaporatorA lli-gis connected to, an; economizer section 22 comprising a tubular flow path 23vpositionedin the p ailli` ofgyflQW of the gases beyond the second evaporator section I9 in the directionl of floW of said gases. The inlet 24.0f the economizer is connected .to a A,feed water inlet pipe 25 kthrough a.V control valvel. Feed line 25 is connected at one end -to the discharge of a feed pump 25. the suction of.. Which -.pump is in communication. withA acontainer B contain;

. ing feed water.

A superheater 23 is positioned in the .sett ing IU in the path yof liow'of the gases of combustion at a point intermediate the evaporator' sections I5 and I9. The superheater inlet29 ism-cem,- munication .with the ,feed water line. 215 thrgllgh. aconduit controlled byvawater injection--valve 3l` so that thesuperheated steam temperature may` bel controlled by the-injection of cool `feed water.

Feed Waterline25 is. also in communication With the water turbine l5I of a lirstseparating and circulating meansv 32 for delivering Water to the evaporator or first vapor generating sec,- tion I5. The rst separating and circulating means ,or device 321 comprisesV anelongated Yver.- tically disposed housing 33 :l having a fluid ,vc/hamber 3.4.therein and-agciroulatingpump casingi35` atthe bottom of the'.heusing.v Thelowerfend ofthe'chamber 34 is connected by. a. passage. 38- with a chamber 3.9 inthe casing. The. lower end of the casing 35 is closed by. aecap El having a hollow. extension; 4 I. Cap. 4D; has .an annular flange 42 wh-ich projectsl intothe chamber. 39- and engages a partition 13Y holding it` tightlyy against an annul-ar shoulder 44: to dividethe chamber 39- into two separate chambers,- atcr.- culating pump chamber; 45 and a water turbine chamber 46. A drive shaft llhavirlgareduced lower end portion .48.mounted in a thrustbear-` 5&5'j ing 49' is disposed in the closed end of the cap 40 in Huid-tight relationship thereto and extends through the chambers 34, 45 and 46. A water turbine or auxiliary actuating means 5|, the blades of which extend into the cap 40 is xed to shaft 41 in chamber 46. Chamber 46 has an inlet port 53 which is in communication with the feed water line 25 and an outlet port in communication with an outlet conduit 54 which conducts water to an inlet port 53 of an auxiliary water turbine 5| of a second separating and circulating means or device 55 which, as shown, is identical to the rst separating and circulating device 32.

A circulating impeller or other circulating means 56 is xed to the shaft 41 above the water turbine and in the chamber 45. The impeller 56 has a plurality of blades 58 which are curved downwardly and outwardly from the passage 38 to the periphery of the impeller. Concentrated feed water flows into the impeller from the chamber 34 and is discharged into a concentrated feed water line 51 through a conduit 59. Line 51 is in communication at one end thereof with the inlet |1 of the evaporator section I5 and at the opposite end with a blowdown valve 66.

The upper part of the first separating and circulating device 32 has a separating chamber 6| into which a mixture of steam and water from the first evaporator section l5 is discharged. Steam and water conduit 62 is in communication with the outlet I8 of the evaporator section and with the -chamber 6|, the conduit 62 being connected to said chamber so as to discharge steam and water tangentially thereof. The separating chamber 6| communicates at its lower end with the upper part of the chamber 34. Tubular member 63, of lesser diameter than the chamber 6| and having a passage 64 therein, is disposed in the chamber 6| and, as shown, is provided with a peripheral iiange 65 which maintains the tubular member in position. A mechanical steam and water separator 66 is provided by a plurality of radial blades 61 fixed to shaft 41 in chamber 6| closely adjacent the lower end of the tubular member 63 in the path of steam flowing from the separating chamber 6|. Other forms of separators may be employed. Tubular member 63 projects upwardly into a hollow cap 68, which closes the upper end of the first circulator and separator 32, to a point short of the upper end thereof thereby forming space 69 between the end of the tubular member and the cap. A cylindrical member is secured at its upper end to the upper end of member 63 and extends downwardly of the member 63 in spaced relationship to the inner wall thereof to provide an annular steam by-pass passage 1|. IThe interior of member 16 provides a main steam passage 12, which communicates with space 69, for steam iiowing from passage 64. A plurality of spaced turbine blades 13 at the lower end of the member 16, and a plurality of rotatable blades 14 fixed to shaft 41 above the blades 13 provide driving means for actuating the other cir-culating means 56 which driving means comprises a steam turbine 15 which is operated by steam iiowing from passage 64 into passage 12.

Means for rendering the auxiliary actuating means 5I operative and inoperative is provided. Steam conduit 16, which conducts steam from the iirst circulating and separating device 32 to the inlet 29 of superheater 28, is connected at its inlet end to space 69 through branch conduit 11 and to passage 1| through by-pass conduit 18, the conduits 11 and 18 being controlled by a slide valve 19 which is operated by pressure responsive device 86. A trap 8l is secured in the lower portion of the chamber 34 above passage 38 and is shaped to provide a passage around the shaft 41 through which water will flow from chamber 34 into the passage 39 and the circulating pump 56.

To insure cooling of the circulating impellers 56 of circulating and separating means or devices 32 and 55 so that flashing and cavitation will be prevented, a relatively small controlled amount of feed water from the feed water line 25 is introduced into said impellers through lines 25' and 25 respectively.

The separating chamber 6| of second circulating device 55 is in communication with outlet 22 of evaporator section I9 through conduit 82 while steam conduit 16' of device 55 is in communication with superheater inlet 29 through line 16. The discharge of the circulating impeller 56 of the device 55 is in communication with the concentrated feed water line 51 through conduit 83. The discharge of auxiliary water vturbine or actuating means 5| of the device 55 is in communication with the source of feed water B through conduit 84'.

The quantity of water delivered to the actuating means 5| and the quantity of steam flowing to the steam turbine 15 is varied in response to variations in the quantity of water delivered to the first evaporator section I5 by the circulating pumps 56 of the device 32. To this end a flow nozzle 85 is positioned in the conduit 59 and pressure conduits 66 and 81 connectv opposite sides of the nozzle 85 with opposite sides of the diaphragm of a pressure responsive device 38 which controls the flow of water in the conduit 25 through a valve 39, conduits 96 and 9| connectng opposite sides of the diaphragm of pressure responsive device 66 with the conduits S6 and 31, respectively. Pressure responsive devices 36 and 86 are so arranged that an increase in flow of circulating water through the conduit 59 will cause the device 88 to operate the valve 89 to decrease the fiow of water through conduit 25 and to the auxiliary water turbine 5| of device 32 and at the same time to cause the device 36 to operate the valve 19 to decrease the iiow of vapor through the by-pass conduit 18 thereby increasing the flow through branch conduit 11 and to superheater 29. A decrease in the iiow of circulating water through conduit 59 will have the opposite effect. Device 55 is controlled in a manner similar to device 32.

In operation, feed water is forced through a conduit 25 by feed pump 26, the amount of feed water entering the inlet 24 of the economizer 22" being regulated by the control valve 26. The remainder of the feed water, except for the small quantity flowing through lines 25' and 25 to insure cooling of impellers 56 of circulating devices 32 and 55 as hereinabove set forth, flowsI through the conduit 25 into the chamber 46 of first circulating device 32 throughthe inlet port 53 and over auxiliary water turbine 5| to rotate shaft 41 and the circulating impeller 56 of said device. Water discharged by the turbine 5| ows through conduit 54 into the inlet port 53 of second separating and circulating device 55 to pass over the auxiliary water turbine 5| thereof thereby rotating shaft 41 and circulating impeller 56 of the device 55. The pump 5| of device 55 discharges water therefrom through the conduit 84 into the feed water supply B. Concentrated Water from the chambers 34 of the devices 32 and 55,v Whichwatery was separated from steamowinginto s`aid'fdevices,l asy will hereinafter be' fully described; flows' downwardly through pas4` sages 38 into the circulating impellers 56, the impeller` 56 of first circulating device 32 forcing the'water through line 59 into concentrated feed Water conduit 51 while impeller 56 of second'circulatingfdevice55 forces' the' water into conduit 83 thence into conduit 5l'. First evaporator section I'V is thereby supplied'with'feed water of high concentration.

FeedV water fiowingrinto the ec'onmizer 22' from the feedA water line 25 flows through the tubular flow path 23 and enters second evaporator vsection I9 through inlet 2l. Steam is generatecl in 1 theevaporator' section bypassage of the `"gases of' combustion over said section, lthe steam flowing fronifiow path 2t through steam outlet 22 into conduit 52 thence into the sep'- ar'atingcliamber 6l of the second circulating and separating device 55'. Steam generated in the first evaporator section I5 flows from the flow path i6 through steam' outlet I8 thence into separating chamber 5| of the first circulating and separating device 32 through conduit 52. Steam generated in said evaporating sections togetherV with unvaporized water flows in a spiral path through the separating chambers 6I, causing the water and solids entrained in the steam to be separated from said steam. The separated water and solids flow downwardly into chambersI 34 wherein the separated solids are deposited in the traps 8| and are removed by blowdowns |03. Separated water ioWs Yinto the lower part of chambers Stand is circulated through lines 83 and'59 respectively by pumps 55 into the concentratedfeed water line 51. The separated steam inrch'ambers 6i flows over'the rotating blades 51 ofthe separators 65 which effects -a further separation of water and `entrainedsolids from the steam;- th'elsteam thereafter flowing upwardly7 thl'oughpassages- 541. Depending upon the position of valves 79, the steamein passages 5d will flow to superheater 28 through-passages 'H and .by-passes- 18 or it will flow to the'superheater 23 throughpassages, chambers 55,'and passages` '11,v or -both thesev` paths of flow. When the generator -is started up,valves 'i5 'are positioned to permit maximum flow' of steam through the by-'passesf-ES 'inasmuch as'y the circulating impeller'sf55 are being driven by the Water turbines 5i. Flow of`V steam from passages 54' into pas.- sages-12 drives turbines 15 and the shafts' 41. 'Ihesteamfiowingthrough passages I by-passesl 78, or-both,flowsthroughconduits 'I6 and 16 intofthe sup'erheater 28 whence it is conducted to the pointof use Steamflowing into passages l2 of the separatingA and circulating devices 32 and 55 will rotate the turbines 'i5 and the shafts 5l at greaterspeed th'an'thatat which vthe shafts are driven by the water turbines 5i so that as soon as steam is prciduced in-sunic-ientquantity to drive the shafts I1-by the turbines 'i5 the speed of shafts 4i will increase'andthe-circulating pumpsV '55 will be dri-'ven *faster and concentrated feed water Will be forced into and through conduits 59 and 83 and conduit 57y thence into the first evaporating section'l5 at a-higher velocity than when the circulating impellers are driven by the water turbines` and at a rate considerably greater than the rate of yevs'np'oration thereof in the evaporating sections l5 andA I9. so V'as to assure sufficient feed waterinthe tubesof-saidsections. This increase 83v and 'fthe flow nozzles-85 thereix'ifcases'the 5ded4 vices 88 to operate vvalves "891' inlines' -25"andl54' toward closedl position therebyl reducing the quantityof Water delivered tothe-:auxiliary turbines 5l. Simultaneously,` the pressure respon# sive devices 8U actuate thevalves 19 to decrease the flow of steam through thefby-passconduits`r I8 and to increase the flowv of steam` to the steam turbines 15 thereby increasing the speedof -rotation of the shafts 41 and the circulating-impellers 55. Consequently, asthe -loadmand the rate of the evaporationA increases, the 'quantity of steam delivered tothe steam turbines-progressively increases and the quantity of Water de livered to the water turbines progressivelyv de'- creases until atv maximum-load`the quantity of wate'1delivered to the 'water' turbines is jsuflicient only to provide substantiallythe minimum circulation in the Water turbine chamber 46 to prevent Aboiling due to churning of the water therein resulting fromthe rotation of thewater turbines.

With this arrangement and operation, it will be perceived that while only highly concentrated' feed water, except for the small quantity of feed water flowing through lines 25 and 25" to insure cooling of impellers 55 of circulating devices 52 and 55 as hereinbeforev set' forth, is" passed through an evaporating section in the" highest temperature zone of a once-through' forced circulation vapor generator, the rate at which thefeed Water is pased'throughl said section is many times the rate of evaporation'thereof in the sections thereby insuring sufficient feed water in the tubes of the evaporator ysections and precluding burning out of'said tubes through dryness caused by lack of Water. The operating lcycle land the control system are effective to conltrol the operation at all loads on the generator vrelative arrangement of the several parts of the apparatus disclosed without departing from the principles of the invention. Accordingly, the

invention is not to be limited excepting by theV scope of the appended claims.

What is claimed is:

1. A once-through forced circulationV vapor generator having a setting, a combustion chamber in the setting, burner means for producing a stream of gases of combustion in the chamber,

means for deliveringliquid under pressure, an

economizer section and at least two vapor generating sections in the setting and in heat exchange relationship with said gases rof combus" tion, said sections being disposed so that the gases F4"flow in heat exchange relationship with said sec-v tions serially, the gases passing in heat exchange relationship with a rst of the vapor generatingv sections before passing in heat exchange rela-r tionship with a second vapor generating section, and flow in heat exchange relationship with the economizer section after flowing vin heat exchange relationship with the vapor generating sections,

the economizer having an inlet andanoutletb the inlet ofthe economizer being in communicae said vapor generating sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through which the mixture of vapor and liquid generated in the respective said vapor generating sections iiows therefrom, the inlet of said second vapor generating section being in communication with the outlet of the economizer, a second vapor and liquid separating means in communication with the outlet of said second of the vapor generating sections to receive the mixture of vapor and liquid therefrom, a second circulating means in communication with said second separating means to receive separated liquid therefrom, said second circulating means also being in communication with the feed liquid inlet means of said first vapor generating section, a first vapor and liquid separating means, said rst separating means being in communication with the outlet of said rst vapor generating section to receive a mixture of vapor and liquid therefrom, a first circulating means in communication with said first separating means to receive separated liquid therefrom, said first circulating means also being in communication with the feed liquid inlet means of said first vapor generating section, vapor actuated driving means for actuating said rst circulating means and said second circulating means, means forming a discharge passage for vapor flowing from said driving means, said driving means being actuated by vapor flowing from the Vapor generating sections through said driving means to said discharge passage, means forming a by-pass for vapor around said driving means, valve means for controlling both said discharge passage and said by-pass to control the quantity of vapor delivered to said driving means, auxiliary actuating means for actuating said rst circulating and said second circulating means, said auxiliary actuating means being driven by liquid under pressure, and means for rendering said auxiliary actuating means inoperative and for moving said valve means to Close the by-pass when the circulating means is actuated by the vapor actuating means and for rendering the auxiliary driving means operative and for moving said valve means to close the discharge passage when the circulating means is not actuated by said vapor actuated driving means.

2. A once-through forced circulation vapor generator having a setting, a combustion chamber in the setting, burner means for producing a stream of gases of combustion in the chamber, at least two vapor generating sections in the setting and in heat exchange relationship with said gases of combustion, said sections being so disposed in relationship to one another that the gases flow in heat exchange relationship with a iirst of the sections before passing in heat exchange relationship with a second section, each of said sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through which the mixture of vapor and liquid generated in the respective said sections flows therefrom, means for delivering liquid under pressure to the inlet of said second section, a second vapor and liquid separating means in communication with the outlet of said second section to receive a mixture of vapor and liquid therefrom, a second circulating means in communication with said second separating means to receive separated liquid therefrom, said second circulating means also being in communication with the feed liquid inlet means of said first vapor generating, section,l separated vapor conduit means in communication with said second vapor and liquid separating means to receive separated vapor therefrom, a first vapor and liquid separating means in communication with the outlet of said first vapor generating section to receive a mixture of vapor and liquid therefrom, vapor outlet means in cornmunication with the rst vapor and liquid separating means to receive separated vapor therefrom, a first circulating means in communication with said first separating means to receive separated liquid therefrom, said rst circulating means also being in communication with the feed liquid inlet means of said first vapor generating section wherebi7 said rst vapor generating section receives liquid separated from the mixture of liquid and vapor generated in said first and second vapor generating sections which liquid constitutes substantially all the feed liquid to be vaporized in said first section, driving means for actuating each of the circulating means to deliver said separated liquid therefrom to the feed liquid inlet means of said first vapor generating section, an auxiliary actuator associated with each of the circulating means, said auxiliary actuators being driven by liquid under pressure, and control means associated with each of said separating means and circulating means and responsive to the flow of liquid from said circulating means to the feed liquid inlet means of said nrst vapor generating section for rendering the auxiliary actuators inoperative when the driving means is operative.

3. A once-through forced circulation vapor generator having a setting, a combustion chamber in the setting, burner means for producing a stream of gases of combustion in the chamber, at least two vapor generating sections in the setting and in heat exchange relationship with said gases of combustion, said sections being so disposed in relationship to one another that the gases ilow in heat exchange relationship with the first of the sections before passing in heat exchange relationship with a second section, each of said sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through which the mixture of vapor and liquid generated in the respective said sections flows therefrom, means for delivering liquid under pressure to the inlet of said second section, a second vapor and liquid separating means in communication with the outlet of said second of the sections to receive a mixture of vapor and liquid therefrom, a second circulating means in communicating With the second separating means to receive separated liquid therefrom, said second circulating means also being in communication with the feed liquid inlet means of said first vapor generating section, separated vapor conduit means in communication with said second vapor and liquid separating means to reecive separated vapor therefrom, a irst vapor and liquid separating means in communicating with the outlet of said first vapor generating section to receive a mixture of vapor and liquid therefrom, vapor outlet means in communication with the first vapor and liquid separating means to receive separated vapor therefrom, a first circulating means in communication with said rst separating means to receive separated liquid therefrom, said first circulating means also being in communication with the feed liquid inlet means of said first vapor generating section whereby said first vapor generating section receives liquid separated fromV ggg, y

`-themixturerof 'liquid and vapor generated in said fvapor `*generating sections which liquid constiftuating each of the circulating means to deliver said separated liquid therefrom to the feed liquid inletmeans of said first vapor generating section, :an auxiliary actuator associated with each of the lcirculating means, said auxiliary actuators being vdriven by liquid under pressure, and control means associated vwith each of said separating and Ycirculating means and responsive to Atheffiovv of liquid from said circulating means, for. rendering thelauxiliary actuators inoperative when lthe .circulating means is actuated by the driving :means andfor rendering the auxiliary actuators operative when the circulating lmeans is rnot-.actuated by said drivingfmeans.

Q4. AA once-through forced circulation-vapor generator having a setting, a combustion chamberV in the setting, burner means for producing a .stream of gases of combustion in the chamber, atleast two vapor generating sections in the setting and in vheat exchange relationship with said gases-of combustion, said sections being so disposed in relationship to one another that rthe gasesflow in heat exchange relationship with a first of `the sections before passing in heat exchange relationship'with a second section, each of said sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through Which the'mixture of vapor and liquid generated in the respective said sections flows therefrom, means for delivering liquid under pressure to the inlet of said second section, a second vapor and liquid separating means in communication with the outlet ofsaid second of the sections to receive a mixture of vapor and liquid therefrom, a second circulating means in communication with the second separating means to receive separated liquid therefrom, said second circulating means also being in communication with the feed liquid inlet means of said first vapor generating section, separated vapor conduit means in communication with said second vapor and liquid separating -means to receive' separated vapor therefrom, va first vapor and liquid separating meansin communication With the outlet of said firstvapor generating section to receive a mixture ofV vapor and liquid therefrom, vapor outlet means in communication With the first vapor and liquid separating means to receive separated vapor -therefrom,.a first circulating means in communication With said first separating means to receive separated liquid therefrom, said first circulating means also being in communication with the feed liquid inlet means of said first vapor generating section whereby said first vapor generating section receives liquid separated from the mixture of liquid and vapor generated in saidu vapor generating sections Which liquid constitutes substantially all the feed liquid to `be vaporized in said first section, vapor actuated driving 'means for actuating each of the circulating means to deliver said separated liquid therefrom to' the feed liquid'inlet means of said first vapor generating section, anr auxiliary actuatorassociated with each of the circulating means, said auxiliary actuators being driven by liquid under pressure, and control means associated With each of said separating and circulating means and responsive to the iiow of liquid from the circulating means for controlling the flow of liquid to said auxiliary actuators and the flow of vapor to said vapor actuated driving means and operative to fio :diminishthe flow of liquid to saidauxiliary actuators and to increase'y the iiow of vaporto said vapor actuated driving means upon an increase in the flow of liquid from said circulating means.

5. A once-through forced circulation vapor generator having a setting, a combustion chamber. inthe setting, burner means for -producinga stream of gases of combustion in'the chamber, at least two vaporgenerating sections in the setting and in heat exchange` relationship with said gases of combustion, said sections being so disposed `in relationship to-one another `that the gases flovvin .heatexchange relationship With a first of the sections before passing in heat'exchangerelationvship with a second section,feach of said sections having feedliquid inlet means through 'which the feed liquid to be vaporized enters said .sections and an outlet throughwhich the mixture of vapor and liquid generated in therespective said sections flows therefroni,-means`for delivering liquid underpressure to theinlet of said second section, -a second vapor vand liquid separating means in communication with the'outlet of said second of the sections to receivepa mixture of vapor and liquid therefrom,'a second circulating means in communication with the second separating means to receive separated liquid vtherefrom, said second circulating means also'beingin communicationwith the feed liquidinlet means of said first vapor generating section, separated vapor conduit means in communication'with said second vapor and liquid separating means to receive separated vapor therefrom, a rst vapor and Aliquid separating-means in communication with the outlet of said-first vapor generating section to receive a mixture of Yvapor and liquid therefrom, vapor outlet means :in communication with the first vapor-,and'liquid separatingv means to receive separated vapor therefrom, aiirst circulating means in communication With Vthefoutlet of -said first separating means to 'receive Yseparated liquid therefrom, said "first "circulating means alsov being -in communication Avvith'the feed liquidinlet means of said rst vapor generating section Whereby said first vapor vgener'- ating section receivesliquid-separated from the mixture of yliquid and vapor generated in said vapor generating sections which liquid lconstitutes substantiallyall the feed liquid to be vaporized in .said firstsection, .vapor actuated driving means for -.actuating each of the circulating means to deliver said separated liquid therefrom to the feed liquid inletmeans of said first vapor generating section, an auxiliary actuator associated with each of the circulating means, said auxiliary actuators being driven by liquid under pressure, and control means associated with each of said separating and circulating means and responsive to the flow of liquid lfrom the circulatingmeans and operative to increase the ,flow of Yliquid tothe auxiliary-actuators and to decrease Athe flow of vapor to the vaporactuateddriving. meansupona decrease in thevow of liquid fromsaid `circulating means, thereby `,to actuate the vcirculating means-by said auxiliaryactuatorsand to increase the iiow ofr .vapor to said vapor actuated driving means and to decrease the flow of liquid to the auxiliary actuators upon an increase in the flow of liquid from the circulating means, thereby to actuate the circulating means by the vapor actuated driving means.

6. A once-through forced circulation vapor generator having a setting, a combustion chamber in the setting, burner means for producing a stream of gases of combustion in the chamber, at

least two vapor generating sections in the setting and in heat exchange relationship with said gases of combustion, said sections being so disposed in relationship to one another that the gases flow in heat exchange relationship with a first of the sections before passing in heat exchange relationship with a second section, each of said sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through which the mixture ofvapor and liquid generated in the respective said sections flows therefrom, means for delivering liquid under pressure to the inlet of said second section, a second vapor and liquid separator in communication with the outlet of said second of the sections to receive a mixture of vapor and liquid therefrom, movable vapor and liquid separating means in the path of flow of the vapor flowing from the second separator, second circulating means in communication with the second separator to receive separated liquid therefrom, said second circulating means also being in communication with the feed liquid inlet means of said first vapor generating section, separated vapor conduit means in communication with said second vapor and liquid separator to receive separated vapor therefrom, second driving means for normally actuating the second circulating means to deliver separated liquid to the inlet of said iirst vapor generating section, a first vapor and liquid separator in communication with the outlet of said rst vapor generating section to receive vapor therefrom, further movable vapor and liquid separating means in the path of ow of the vapor iiowing from the first vapor and liquid separator, vapor outlet means in communication with the first vapor and liquid separator to receive separated vapor therefrom, first circulating means in communication with the rst separator to receive separated liquid therefrom, said rst circulating means also being in communication with the feed liquid inlet means of said first vapor genw erating section, rst driving means for normally actuating said rst circulating means to deliver separated liquid to the inlet of said rst vapor generating section whereby said first vapor generating section receives liquid separated from the mixture of liquid and vapor generated in said vapor generating sections which liquid constitutes substantially all the feed liquid to be vaporized in said one section, an auxiliary actuator associated with each of the circulating means, said auxiliary actuators being driven by liquid under pressure, and control means associated with each of the separating and circulating means and responsive to the ow of liquid from the circulating means to the inlet of said rst vapor generating section for rendering the auxiliary actuators inoperative when the first and second driving means are operative.

7. A once-through forced circulation vapor generator having a setting, a combustion chamber in the setting, burner means for producing a stream of gases of combustion in the chamber, at least two vapor generating sections in the setting and in heat exchange relationship with said gases of combustion, said sections being so disposed in relationship to one another that the gases flow in heat exchange relationship with a first of the sections before passing in heat exchange relationship with a second section, each of said sections having feed liquid inlet means through which the feed liquid to be vaporized enters said sections and an outlet through which the mixture of vapor and liquid generated in the respective said sections flows therefrom, means for delivering liquid under pressure to the inlet of said second section, second separating and circulating means comprising a second housing, vapor and liquid separating means in the second housing, said separating means being in communication with the outlet of said second of the sections to receive vapor therefrom, a second circulating pump in the second housing, said second circulating pump being in communication with the separating means to receive separated liquid therefrom, said pump being in communication with the feed liquid inlet means of said rst vapor generating section, a second vapor actuated turbine in the second housing for driving the second circulating pump, a second liquid actuated means in the second housing constituting second auxiliary means for driving the second circulating pump, rst separating and circulating means comprising -a first housing, vapor and liquid separating means in the rst housing in communication with the outlet of said first vapor generating section to receive vapor therefrom, a rst circulating pump in the first housing in communication -With the feed liquid inlet means of said rst vapor generating section whereby said rst vapor gener-ating section receives liquid separated from the mixture of liquid and Vapor generated in said vapor generating sections which liquid constitutes substantially all the feed liquid to be vaporized in said iirst section, a vapor actuated turbine in the rst housing and constituting normal means for driving the circulating pump in said first housing, liquid actuated means also in said first housing and constituting auxiliary means for driving said rst circulating pump, and control means associated with each of said separating and circulating means for rendering its auxiliary liquid actuated means inoperative when its circulating pump is actuated by its vapor actuated turbine and for rendering its auxiliary liquid actuated means operative when its circulating pump is not actuated by its vapor actuated tur bine.

MARTIN FRISCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,835,610 Page Dec. 8, 1931 1,860,363 La Mont May 3l, 1932 1,883,293 Jacobus Oct. 18, 1932 2,170,348 Dickey Aug. 22, 1939 2,321,390 Juzi June 8, 1943 2,405,573 Frisch Aug. 13, 1945 

